1. Field of the Invention
The present invention relates to a spring that is provided between a first member and a second member for inhibiting transmission of high-frequency vibration therebetween, and in particular relates to an improvement in a shape of the spring.
2. Related Art
In a variety of fields of such as automobiles, precision equipment, home electrical appliances and architectural industries, techniques for inhibiting transmission of vibrations are required. The techniques for inhibiting transmission of vibrations are applied to engines, motors rotating at high speed, dewatering bins of laundry machines and constructions, etc. As a technique for inhibiting transmission of vibration, a natural vibration frequency of a system composed of an object and a supporting portion is set at a sufficiently lower degree than a predetermined vibration frequency range. As a method for this setting, a constant of a spring in the supporting portion may be reduced. In this case, when the constant of the spring is reduced, the size of the spring must be increased for supporting a load thereat.
A method in which a disc spring is used between the object and the supporting portion is proposed (For example, see Japanese Patent Applications, First Publication No. 5-172171 and First Publication No. 2002-54685.). Loading characteristics of a disc spring are designed as a curve shown in FIG. 6, so that not only can the load be supported, but also an area A can be set on the curve, and the constant of the spring can be reduced when the loading characteristics thereof are within the area A.
When a disc spring is deformed in a substantially flat shape by an applied load, edge portions of an inner circumference and an outer circumference thereof slide with respect to counter members, whereby friction occurs. Therefore, when a range of use of the disc spring is set within the area A shown in FIG. 6, hysteresis shown in FIG. 7A occurs on the practical loading curve. As a result, the practical dynamic constant of the disc spring in the range of use thereof is determined according to an inclination of a diagonal line between points P and Q in FIG. 7. In this case, when a fluctuation of in the range of use is set at a small degree, as shown in FIG. 7B, the inclination of the diagonal line is increased, so that the dynamic constant of spring is increased. In a system in which such a disc spring is used, when a fine vibration such as a high-frequency vibration is provided, the dynamic constant of the spring is increased, so that the natural vibration frequency of the system is increased. As a result, transmission of the high-frequency vibrations cannot be inhibited.